In my opinion, separating lust and masturbation is possible, but it's not easy. It takes a great deal of committment, especially to God. It also takes time, because once a person's mind is exposed to lustful images, it adjusts to that, and develops a "pattern of response" if you will. In order to accomplish this, you need to ask yourself two questions: (1) Why do I want to separate lust and masturbation?; and (2) how much am I willing to sacrifice (mentally, emotionally, and spiritually) to bring about that result?
I'll be honest with you: I first got hooked on this activity when I was about 14 years old, and from the ages of 16 to 26 I battled a porn addiction. I spent many, many days over the last year of it or so, trying like crazy to figure out why I kept getting trapped so easily...and the answer was that I was afraid to let go of the lust. You see, I had grown up extremely sheltered throughout my life, rarely having any long-term friends to speak of. Emotionally, I was a recluse, and when puberty hit I felt all the worse. Suddenly, all these crazy emotions and desires were racing through my mind and body, and I didn't know what to do with them. I had no positive male role models, and all the kids at school just made fun of me, so I internalized my sex drive, thinking no one could possibly love me if they knew what I was thinking.
At the beginning, my addiction started with "erotic thrillers" on late-night cable. At the time, it seemed like those films created a "world" in my mind where I could release all these thoughts, without feeling rejected for them...but it was an illusion, and as my thoughts became more explicit the addiction escalated. I wound up "graduating" to written erotica, then Playboy, then online porn. Lust is like any other addiction; it feeds on fuel. For me, one of the keys to conquering it was letting go of the "false reality" created by my fantasies, and the sense of security they provided. I had to admit to myself, "All this condemnation, shame, and guilt isn't worth the thrill anymore." If you keep books, videos, or images around you which foster lustful responses, conquering that addiction is next to impossible. You need to get to a point where you honestly don't want the lust anymore. In my case, I threw out my Playboy collection, deleted all the porn videos off my computer, and trashed all the erotic stuff I'd written down. However, that alone won't set you free - only the love of Jesus can do that. Is it easy? NO!!! Your flesh will claw at you night and day, desperate to regain what you've given up. I've been porn-free almost 4 years now, and I still battle lustful thoughts almost every day. I keep surrendering them to God, and I keep repeating Bible verses to myself, reminding me that I'm loved by God, and that I don't have to go through this alone.
Now, how does all this relate to the practice of masturbation? Well, as your desire to engage in willful lust gets lower, you may find it easier to release the physical tension without giving in to your old patterns of thinking and feeling. People say, "even the little thoughts count", and to that I'd say they're both right and wrong. We can't choose which thoughts pop into our brains, even while masturbating...but we can choose whether or not they stay there. It takes effort and a desire to serve God more than yourself, but over time it becomes easier to 'kick" lustful thoughts out of your mind.
I can almost hear the cries now: "Heretic! Evildoer! Ungodly heathen!" To all of that, I respectfully say, "Shut up. Unless you've walked this path yourself, you're not the best person to be ordering people around." Lust is definitely sin, there's no argument about that...but not all sexual thoughts are lustful. What i mean is this: to fantasize about having any kind of sexual contact with a person you're not married to is lust, and therefore sinful. However, what about focusing on your own body, or the God who gave you a sex drive to begin with? It's not easy - I repeat, NOT EASY - but I do believe its possible. God says in the Bible that He will not allow us to be tempted beyond what we can bear, and that He will provide a way of escape. So, what if masturbation, in and of itself, isn't an activity to be feared or hated, but to be used wisely as a "preventive measure" for those who are not married?